I had only around 100 hands from both villians, and they both fold sqeeze 3/3, 4/4, so I did it as pure bluff.
Once he calls, should I cbet considering his range is strong, and all small cards?
On turn I call because we are deep, but does it mean anything, because if I hit flush on river, I will hardly get some additional money in, so should I fold turn?
And river is interesting, I was not sure if I should bet small for thin value, because most likely he has 99+ with which he checks behind.

Postflop: As played why not bet/fold the river? Villains range will most likely have PPs that check back the river.

Back to the flop/turn play. I'd ck/fold that flop as I doubt we have a ton of FE unless he is fit/fold postflop. Turn ck/call is also marginal because we get 25% pot odds but we mostly have 24% equity if we count our Ax. And our implied odds are marginal at best.

I don't understand your reason, why not to sqeeze bluff against a player who folds a lot to sqeeze and we are deep?
Anyway, I consider it as bluff, so I am not going to play for full stacks unless I hit nuts.
I think if he folds a lot preflop, it is already profitable to sqeeze.